ABSTRACT
An important step in several bioanalytical applications is the immobilization of biomolecules. Accordingly, this procedure must be carefully chosen to preserve their biological structure and fully explore their properties. For this purpose, we combined the versatility of the layer-by-layer (LbL) method for the immobilization of biomolecules with the protective behavior of liposome-encapsulated systems to fabricate a novel amperometric glucose biosensor. To obtain the biosensing unit, an LbL film of the H2O2 catalyst polypeptide microperoxidase-11 (MP-11) was assembled onto an indium-tin oxide (ITO) electrode followed by the deposition of a liposome-encapsulated glucose oxidase (GOx) layer. The biosensor response toward glucose detection showed a sensitivity of 0.91±0.09 (µA/cm2)/mM and a limit of detection (LOD) of 8.6±1.1 µM, demonstrating an improved performance compared to similar biosensors with a single phospholipid-liposome or even containing a non-encapsulated GOx layer. Finally, glucose detection was also performed in a zero-lactose milk sample to demonstrate the potential of the biosensor for food analysis.
Subject(s)
Biosensing Techniques/methods , Glucose Oxidase/chemistry , Glucose/analysis , Liposomes/chemistry , Peroxidases/chemistry , Aspergillus niger/enzymology , Biocatalysis , Capsules , Electrochemistry , Enzymes, Immobilized/chemistry , Enzymes, Immobilized/metabolism , Glucose/chemistry , Glucose Oxidase/metabolism , Hydrogen Peroxide/chemistry , Models, Molecular , Molecular Conformation , Polyethyleneimine/chemistryABSTRACT
Thin films of cobalt phthalocyanine (CoPc) were deposited onto solid substrates through physical vapor deposition (PVD) by thermal evaporation up to 60 nm thick to determine their molecular architecture and electrical properties. The growth was monitored using UV-Vis absorption spectroscopy, revealing a linear increase for absorbance versus thickness. PVD films were found in the crystalline alpha phase and with the CoPc molecules forming ca. 45 degrees in relation to the substrate surface. The film surface was fairly homogeneous at the micro and nanoscales, with the roughness at ca. 3 nm. DC and AC electrical measurements were carried out for devices built with distinct structures. Perpendicular contact was established by depositing 60 nm CoPc PVD films between indium tin oxide (ITO) and Al, forming a sandwich-type structure (ITO/CoPc/Al). The current versus DC voltage curve indicated a Schottky diode behavior with a rectification factor of 4.2. The AC conductivity at low frequencies increased about 2 orders of magnitude (10(-9) to 10(-7) S/m) with increasing DC bias (0 to 5 V) and the dielectric constant at 1 kHz was 3.45. The parallel contact was obtained by depositing 120 nm CoPc PVD film onto interdigitated electrodes, forming an IDE-structured device. The latter presented a DC conductivity of 5.5 x 10(-10) S/m while the AC conductivity varied from 10(-9) to 10(-1) S/m between 1 Hz and 1 MHz, respectively, presenting no dependence on DC bias. As proof-of-principle, the IDE-structured device was applied as gas sensor for trifluoroacetic acid (TFA).
ABSTRACT
Twenty-four hirsute female patients were treated with 100 mg of depo-medroxyprogesterone acetate intramuscularly every 15 days. Twenty-three showed definite improvement from their abnormal hair growth. All patients with initially elevated 17-ketosteroids in 24-hour urine collections showed a decrease of these metabolites with treatment. In eleven patients the initial plasma testosterone level was elevated and returned to normal values with treatment. The first patient who was submitted to this therapy stopped the treatment for 5 months and started having abnormal hair growth again. With other patients, after initial treatment with depo-medroxyprogesterone acetate intramuscularly, we started using contraception pills containing medroxyprogesterone; this maintained the reduced ectopic hair growth. The most important side effect was amenorrhea.
